There has been disclosed a multi-function apparatus in which, in a case where user information is input to the multi-function apparatus, the multi-function apparatus makes an authentication server perform authentication on the user information. If the authentication on the user information succeeds, the multi-function apparatus obtains card information from a card brought into contact with a card reader of the multi-function apparatus and supplies the card information to the authentication server. The authentication server registers the card information in association with the user information. Therefore, a user can log in to the multi-function apparatus by bringing the card into contact with the card reader of the multi-function apparatus, without inputting the user information to the multi-function apparatus.